This invention relates generally to electrical contacts and in particular to those having means for preventing warpage thereof, an assembly including a supporting member and such electrical contact, and a method of mounting such electrical contact on the supporting member.
In the past, various electrical switching means were provided with a supporting member, such as a power conducting terminal or buss or a generally thin, resilient metal switch blade or contact operating arm to which an electrical contact was mounted. When the electrical contact was mounted on the switch blade, it was movable or pivotable under preselected conditions between a making position engaging its contact with a stationary contact mounted on a stationary switch blade or buss and another or breaking position disengaged therefrom. Some of the past electrical contacts were formed from a metal or metal alloy having relatively high conductive characteristics, such as silver or an alloy thereof or the like, and a centrally located rivet or deformable stem was integrally formed on the past electrical contacts for mounting them to the switch blade. To effect such mounting, the integrally formed rivet was passed through an accommodating opening in the switch blade to position the electrical contact generally in face-to-face relation with one side of the switch blade, and the rivet was then deformed or staked over into displacement preventing engagement with the opposite side of the switch arm. One of the disadvantageous or undesirable features of the past electrical contacts and the assembly thereof to a switch blade is believed to be that under some load conditions, the past electrical contacts were subject to curling or warping. The phenomenon of contact curling or warping was occasioned in response to heat generated in the contact upon the application of power thereto causing at least a marginal or peripheral portion or edge thereof to be displaced or move away from the power carrying switch blade. Another disadvantageous or undesirable feature of such past contact and the assembly thereof to a switch blade is believed to be that upon the occurrence of such curling or warping, the gap between the contact and its associated mating contact could be reduced to zero and/or the contacts could become welded to each other. Of course, a past solution to this problem of contact curling or warping with respect to a riveted type contact was to either increase the thickness of the contact and/or increase the diameter of the mounting rivet thereof; however, either of these solutions also involved the ancillary disadvantageous features of increasing the size of the contact as well as the cost thereof.
Also in the past, laminated contacts were brazed, welded or otherwise fixedly engaged generally at a single generally central location with a switch blade therefor, but some of the laminated contacts and the assembly thereof to the switch blade also involved substantially the same disadvantageous or udesirable feature of curling or warping, as previously discussed hereinabove. An ancillary disadvantageous feature with respect to the utilization of the past laminated contact is believed to be that precious metals were laminated to a base conductive metal thereby to appreciably increase the cost of the laminated contact relative to the above discussed prior art rivet type contact. Still another ancillary disadvantageous feature with respect to the utilization of laminated contacts is believed to be that it was more costly to attach by brazing or welding or the like than to rivet the rivet type contact. Further, another disadvantageous or undesirable feature of the past laminated contact and its assembly to the switch arm is believed to be that the precious metal sometimes delaminated from its base metal upon the occurrence of the curling or warping phenomenon. Still another disadvantageous or undesirable feature of both the past rivet type contact and the laminated contact and their respective assembly with their switch blades is believed to be that it was sometimes necessary to provide a back-up washer or the like for strengthening the switch blade to support the contact. Of course, another past solution to the curling or warping problem was to utilize a laminated type contact having multiple welding projections generally adjacent the peripheral portion of the laminated contact, and these multiple welding projections were welded to a switch blade; however, one of the disadvantageous features of this particular type of laminated contact is believed to be that the precious metal laminate thereof made it more costly than the aforementioned rivet type contact.